Is there a relationship between exposure to trace concentrations of waste anesthetic gasses and the development of health concerns? After two independent groups analyzed more than seventeen studies, including one well-designed prospective study, the consensus is that there is no risk of adverse health effects to personnel where waste anesthetic gases are scavenged.

Studies published in the late 1960’s and early 1970’s pointed to waste anesthetic gas (WAG) as a direct contributor to everything from fatigue, exhaustion, and headaches to cancer, infertility, spontaneous abortion, and birth defects. These studies resulted in a 1974 National Institute for Occupational Safety and Health (NIOSH) recommendation that waste anesthetic gas be scavenged in all areas. Three years later NIOSH recommended that WAG exposure standards be established.

In the 1980’s, researchers examined the conclusions drawn from these earlier studies. Seventeen studies were examined and all were found to have flaws. They found that the results of these studies could have been influenced by confounding variables such as occupational stress, and exposure to blood, drugs, aerosols or radiation. Even the wording of the questionnaires and the inability to verify reported outcomes by the responders may have influenced the conclusions drawn from the earlier studies. One prospective study using annual questionnaires, surveyed all British female medical school graduates working in hospitals during the years 1977 to 1984. Analysis showed that female anesthesiologists had no increased risk of infertility. Another study using Finnish National Health Registry data demonstrated no statistical differences between patients who had been exposed to WAG and those who had not, when medical records were examined.

However, even with the flaws in the early WAG studies, some good came out of them: waste anesthetic gas is now scavenged. A 1992 study in the New England Journal of Medicine and a later study in the American Journal of Epidemiology reported reduced fertility and increased spontaneous abortion among dental assistants employed in practices where nitrous oxide was not scavenged. And despite the fact that the modern anesthetic gases of halothane, isoflurane, enflurane, sevoflurane and desflurane are believed to be harmless in trace concentrations, their predecessors were once thought to be safe as well. Up until 1977 trichloroethylene and fluroxene were used as general anesthetics and thought to be safe. Chloroform before that. But none of the three are now in use as anesthetics because they were found to be hepatotoxic, mutagenic and carcinogenic.

The bottom line is that it’s important to scavenge waste anesthetic gases. It’s also important to stay mindful to otherwise reduce your exposure to waste gases. And finally, implement an education program for all personnel working in these areas. Studies have shown that with these procedures in place, trace anesthetic gasses can be maintained below the levels recommended by NIOSH and OSHA.

Ken Crump (kencrump.com) is a writer and animal anesthetist and writes Making Anesthesia Easier for Advanced Anesthesia Specialists. He makes dozens of Continuing Education presentations on veterinary oncology and anesthesia across the United States and in Canada. Ken retired from Colorado State University in 2008.